Abstract

Both experimentally and with computer simulation, we study soliton propagation in an all-optical long-distance communications system where fiber loss is periodically compensated by Raman gain. We find that the fidelity of soliton transmission is a function of the ratio L/z₀, where L and z₀ are the amplification and soliton periods, respectively: pulse distortion shows a peak near z₀ = L/8, whereas the soliton is well preserved everywhere for z₀ ≪ L/8. Finally, for z₀ ≫ L/8, although not preserved everywhere, the soliton is recovered periodically with the pulse energy. We also describe optimal system design based on the exceptional pulse stability and low soliton powers to be had in the region z₀ ≫ L/8. Typical amplification periods are in the 30–50-km range, pump powers are <100 mW, and for bit rates in the 10-GHz range, time average signal powers are at most a few milliwatts. The single-channel rate-length product for error rate <10⁻⁹ is ~29,000 GHz/km. Finally, we show that in the gain-compensated system with wavelength multiplexing, soliton-soliton collisions produce random modulation of individual pulse velocities. Nevertheless, multiplexing can yield rate-length products >300,000 GHz/ km.

© 1985 Optical Society of America